Objective To evaluate the feasibility and safety of transumbilical laparoendoscopic sin-gle-site dismembered pyeloplasty ( U-LESS-P ) for the treatment of ureteropelvic junction obstruction (UPJO). Methods Between Mar.2011 and Mar.2012, U-LESS-P was performed in 8 consecutive pa-tients with UPJO by one experienced laparoscopic surgeon .The patients included 5 males and 3 females, with an average age of 28 (16-45) years.Of the 8 patients, six presented with flank pain , and two were a-symptomatic and discovered incidentally by health check .Of the 8 patients, seven had UPJO on the left side and one on the right side .The diagnosis was established by renal ultrasonography , diuretic renal scan , intra-venous urography (IVU) or/and computed tomography urography (CTU).Renal ultrasonography, IVU and ( or) CTU showed hydronephrosis and UPJO in the affected side , while diuretic renal scan demonstrated re-nal function deteriorated .No patients had undergone abdominal surgery previously .A 2-2.5 cm umbilical in-cision was made for single-port access .The procedures were performed using 30°5 mm or 10 mm laparoscope with a combination of conventional and bent laparoscopic instruments . Results All procedures were com-pleted successfully .None was converted to open surgery or traditional laparoscopic surgery .The mean opera-tive time was 153 (117-190) min, and the average estimated blood loss about 20 (10-40) ml.The mean time to resume oral diet was 1.5 days.The drainage remained 2-7 days.The mean hospital stay was 6 (4-8) days.With the follow-up of 3-6 months, symptom-free was investigated in all 8 cases.Ultrasonography , diuretic renal scan and IVU showed decreased or disappeared hydronephrosis .No operative complication , such as anastomotic stoma stenosis , was founded . Conclusions U-LESS-P is a safe and effective proce-dure for the treatment of UPJO , with the advantages of decreased operative morbidity , postoperative rapid re-covery and improved cosmetic result . Key words: Transumbilical; Single-site; Laparoscopic surgery; Dismembered pyeloplasty; Ureteropelvic junction obstruction